Grit chamber designs recommend a detention duration of_______________?
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Answer: A. 1 minute
Explanation
Grit chambers maintain low horizontal velocities to allow dense inorganic sand particles to drop out. A short detention duration of approximately one minute prevents lighter organic solids from settling. Rapid passage ensures only heavy grit accumulates while organic matter remains suspended for treatment. Raw sewage contains abrasive grit particles that can damage downstream mechanical pumps and valves. Detention time refers to the average amount of time wastewater spends inside a treatment basin. Horizontal velocity in grit channels is typically controlled at around thirty centimeters per second.
Wastewater treatment facilities install grit removal systems at the very beginning of the treatment train. Removing abrasive grit protects mechanical equipment from premature wear and operational failure. Effective grit separation reduces the accumulation of inert material in downstream biological reactors. Two minutes of detention time would allow unwanted organic solids to settle out with the grit. Three minutes is excessive and causes unnecessary accumulation of putrescible organic waste in chambers. Five minutes transforms the grit basin into a primary settling tank, trapping organic sludge.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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